Silicon light trap devices

Abstract

Embodiments relate to buried structures for silicon devices which can alter light paths and thereby form light traps. Embodiments of the lights traps can couple more light to a photosensitive surface of the device, rather than reflecting the light or absorbing it more deeply within the device, which can increase efficiency, improve device timing and provide other advantages appreciated by those skilled in the art.

Description

TECHNICAL FIELD[0001]The invention relates generally to silicon devices and more particularly to optoelectronic silicon devices.BACKGROUND[0002]In optoelectronic devices, light rays are absorbed and generate charge carriers within the device. These charge carriers typically are desired to be generated within a particular light ray absorption region, which can be defined by a depth within the device, such that they can be collected near the surface of the device.[0003]Charge carriers generated deeper than the depth of this region can be thought of us undesirable noise. Conventional approaches to dealing with these charge carriers often relate to transporting them to the surface by extended electric fields or annihilating them by the targeted introduction of recombination centers. The former is not suitable in all situations, such as those with regions that must remain free of electrical fields for physical reasons, and is also limited by available voltage, while the latter reduces in...

AI Technical Summary

Problems solved by technology

Charge carriers generated deeper than the depth of this region can be thought of us undesirable noise.

The former is not suitable in all situations, such as those with regions that must remain free of electrical fields for physical reasons, and is also limited by available voltage, while the latter reduces internal quantum efficiency and can be technically difficult to realize at very high doping atom densities.

Reduced quantum efficiency in turn can affect devices dimensions, and increased complexity and technological challenges can increase costs, which are undesired.

With the increasing depth of penetration, for time critical applications, the delay of slow diffusion currents from the greater depth to which the infrared light penetrates to the surface of the devices is slow.

This can create time delays that become significant in view of the greater time required for the slow diffusion currents to reach the surface.

However, these electrical confinement efforts can become costly and can increase production costs to a level that is economically unfeasible.

In the prior art, such as proximity sensors or time of flight sensors, losses of quantum efficiency are accepted in most cases.

However, these techniques are unsuitable for use in CMOS integrated circuit applications because of the structures themselves.

As discussed above, this can be difficult because silicon as an indirect semi-conductor absorbs infrared wavelength spectral light components only weakly.

In situations where it is beneficial for photo generated charge carriers to be collected near the surface of the semi-conductor, this property of the material can be problematic for time critical device operation.

These electric fields are built up in lightly doped zones and are limited by the available voltage.

This approach leads to reduced quantum efficiency and is technologically difficult to implement at very high impurity atom densities.

Under the circumstances, the recombination active zone is overgrown with a lightly doped epitaxial layer, which is readily susceptible to being dislocated on such a support.

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